This invention relates to a material transport system including loss-in-weight feeders and their control systems.
In some bulk material transport systems some materials, when put into a material container, do not flow out consistently and uniformly without some assistance. In one example, a difficult material may form a self-supporting arch or bridge in the material container, which completely blocks the flow of material to a feeder at the outlet of the material container. The feeder may discharge the loose material below the bridge and then material flow from the feeder may stop even though there is a great deal of material still in the material container. A second failure mode is referred to as a rat hole, which is a narrow vertically oriented tunnel through the material. A rat hole often forms above a bridge and provides a restricted material flow path to the feeder at the outlet of the material container. The result is a sporadic or limited flow of material to the feeder as material from the top surface falls into the rat hole. Usually the flow stops long before the material container is empty. Lesser degrees of these conditions also occur. In these cases, a bridge or rat hole may form and later collapse spontaneously. Although material flow to the feeder may not be stopped completely it still affects the consistency of the feeder performance.